A box of this general type, made of synthetic sheet material, has been described for example in U.S. Pat. No. 3,163,319. The side and rear walls of the prismatic box, which has a rectangular horizontal outline, have a U-shaped top ledge provided with an upstanding marginal ridge which is outwardly offset from the side and rear edges of the bottom wall to embrace the lower part of an identical second box stacked thereon. The box also has a front wall which rises with a forward slope from the bottom wall and forms at an upper edge thereof a forwardly bent handgrip which is also the lower boundary of the aforementioned access opening.
In order to stiffen such a box against lateral spreading of its sidewalls under the weight of overlying boxes of a stack, it is customary--as also shown in the above-identified U.S. patent--to provide these sidewalls in the region of the front wall with hollow upright corner profiles defining the lateral boundaries of the access opening. In order to be able to retain a closure plate in that opening, these corner profiles must have suitable formations enabling the insertion and withdrawal of such a plate.
When an individual container of this description is placed on a shelf, there is usually enough room between its top ledge and the next-higher shelf to enable the insertion and removal of a cover plate receivable in a pair of vertical guide grooves on opposite sides of the access opening. In the case of stacked containers, however, there is not enough clearance with conventional constructions to allow for the necessary vertical sliding motion. In such instances the closure plate may be designed as a hinged flap swingable about a horizontal pivotal axis to serve as a dust cover. Difficulties are, however, encountered in securing such a flap in its closed position, especially when the container must take a bumpy ride on a roller conveyor or is otherwise subjected to rough handling during transportation. An untimely release of the dust cover may then lead to spillage of the contents if the box is filled above the level of the handgrip.